Today, manned and unmanned aircraft can be equipped with automatic or semiautomatic landing systems. To control the approach for landing, automatic landing systems can determine the distance of the aircraft from the intended landing point, for example from a positional or range measurement. With the aid of the distance parameters and other measured variables, such as flight velocity, for example, flight control commands can be generated and the autopilot controlled such that the aircraft sets down at the landing point.
Automatic landing systems for manned aircraft are usually equipped with rangefinders with a high level of integrity and precision. If the landing system is not available or is faulty, the pilot can perform a manual landing there or at an alternate aerodrome (alternate). In unmanned aircraft, in the event of an error in the automatic landing system, the landing can be performed via manual or direct control commands that are transmitted by data link to the aircraft.